Flow control valves are useful for fluid control applications wherein the volume and flow rate of the fluid must frequently be varied. This type of control valve operates by varying the size of the flow passage to allow more or less fluid to flow therethrough. Typically, a flow control valve includes a valve actuator, a modulating element, a valve positioner, and a valve body, which all cooperate to regulate fluid flow.
The valve body generally houses or supports a passage for fluid to pass therethrough, as well as the modulating element such as, for example, a drum, plug, globe, ball, butterfly or the like, which may be moved to change the rate of fluid flow through the valve body. The valve actuator is connected to the modulating element to manipulate the same, and the valve positioner ensures that the valve has achieved the desired degree of opening to enable the desired fluid flow therethrough.
One drawback with conventional flow control valves occurs when the fluid flow passage size is changed to vary the flow rate. If the sectional shape of the passageway changes as the size of the passage changes, such as happens when circular passageways are eclipsed, flow dynamics likewise change. Further, the change in flow with such valves is not linear with the change in size of the passage.
One conventional valve design includes an adjustable drum that may be moved to vary flow through the valve. However, this design shares a shortcoming with many control valves insofar as it includes a linkage between a handle connecting to the drum modulating element and the valve actuator. This linkage or armature inherently includes some play that must be overcome when the actuator is energized to move the handle, resulting in control hysteresis that lowers control accuracy.
Other conventional valve designs include actuators directly engaging “non-drum” modulation elements, thus contributing to improved accuracy. However, these designs suffer limitations in adjustability arising from the modulating element being inherently less adjustable.
There remains a need for a flow control valve having improved adjustability and accuracy. The present disclosure addresses this need.